PROneurotrophins and CONSequences

Neurotrophins as Potential Biomarkers for Active Disease and Poor Outcome in Pediatric Acute Lymphoblastic Leukemia

BACKGROUND

Neurotrophins (NTs) are pivotal growth factors in cellular development and survival. Their precise implications in Acute Lymphoblastic Leukemia (ALL) remain unclear.

METHODS

Pediatric ALL samples (2011-2021) were analyzed from a Southern Brazil cohort. Neurotrophin levels were quantified via ELISA, with survival analysis using Kaplan-Meier curves. Gene expression data were sourced from public genomic repositories and analyzed with R software version 4.0.5.

RESULTS

At diagnosis, pro-BDNF, BDNF, and NGF levels were significantly lower than in healthy controls. Reduced pro-BDNF correlated with unfavorable outcomes. NGF and sortilin were highly expressed in healthy samples, while BDNF and p75NTR were predominant in T-ALL and B-ALL, respectively.

CONCLUSIONS

Neurotrophins show significant alterations in the tumor microenvironment of pediatric ALL. Further studies are needed to elucidate their precise role and prognostic potential.

BDNF and proBDNF serum levels during antidepressant treatment in adolescent girls with a first-lifetime episode of depression: A prospective case-controlled study

INTRODUCTION

As one of the most promising biomarkers in depression course and treatment, the brain-derived neurotrophic factor (BDNF) has been identified as a possible predictor of antidepressant treatment outcomes in the adult population. However, studies on this subject in the developmental population are lacking. We aimed to verify the changes in serum BDNF, proBDNF, and BDNF/proBDNF ratio levels during antidepressant treatment in adolescents diagnosed with depressive episodes. We also investigated these parameters as predictors of antidepressant treatment outcomes.

MATERIAL AND METHODS

Thirty female inpatients, aged 11-17, diagnosed with a first-lifetime depressive episode were assessed at two time-points: before (t0) and after (t1) the period of antidepressant treatment and compared with thirty age-matched healthy girls. The assessment at t0 and t1 involved BDNF and proBDNF serum levels (analyzed with the ELISA method) and standardized depressive symptoms scales.

RESULTS

BDNF serum levels decreased significantly with the antidepressant treatment in the studied group (p = 0.0224). This effect was still present in the subgroup of responders (p = 0.0179) but not among non-responders (p = 0.2184). Responders had a significantly higher initial BDNF/proBDNF ratio than non-responders. The BDNF/proBDNF ratio at t0 could predict the remission status at t1 with a sensitivity of 66.67 % and a specificity of 81.25 % (p = 0.0327).

CONCLUSIONS

BDNF serum levels tend to decrease with successful antidepressant treatment in adolescent girls treated for the first episode of depression. Pretreatment BDNF/proBDNF ratio should be considered a possible biomarker predictive of antidepressant treatment response in adolescent girls.

Neurotrophin peptidomimetics for the treatment of neurodegenerative diseases

Neurotrophins, such as nerve growth factor and brain-derived neurotrophic factor, play an essential role in the survival of neurons. However, incorporating better features can increase their therapeutic efficacy in neurodegenerative diseases (NDs). Peptidomimetics, which mimic these neurotrophins, show potential for treating NDs. This study emphasizes the use of peptidomimetics from neurotrophins for treating NDs and their benefits. By improving bioavailability and stability, these molecules can completely transform the therapy for NDs. This in-depth review guides researchers and pharmaceutical developers, providing insight into the changing field of neurodegenerative medicine.

Biomarkers of Depression among Adolescent Girls: BDNF and Epigenetics

Alterations in brain-derived neurotrophic factor (BDNF) expression have been suggested to mediate the influence of environmental factors on the emergence of depression through epigenetic modifications. However, research on this subject in the developmental population is lacking and the pathophysiology of adolescent depression remains unclear. We aimed to investigate the alterations in BDNF expression and global DNA methylation in depression among adolescent girls. Thirty female inpatients with the initial diagnosis of depression were assessed before and after the period of antidepressant treatment and compared with thirty age-matched healthy controls. The assessment involved BDNF and proBDNF serum levels, the BDNF gene exon IV promoter methylation, and global DNA methylation. The methylation level in the BDNF gene exon IV promoter was significantly lower in the studied group compared with the control and correlated negatively with the severity of depression. The test distinguished the studied group from the controls with a sensitivity of 37% and specificity of 90%. The differences were no longer present after the period of antidepressant treatment. No differences in the global DNA methylation, BDNF, and proBDNF levels were found. We concluded that decreased methylation in the BDNF exon IV promoter could be considered as a biomarker of a depression state among adolescent girls.

The intriguing role of platelets as custodians of brain-derived neurotrophic factor

A State of the Art lecture titled "Platelets and neurotrophins" was presented at the International Society on Thrombosis and Haemostasis Congress in 2023. Neurotrophins, a family of neuronal growth factors known to support cognitive function, are increasingly recognized as important players in vascular health. Indeed, along with their canonical receptors, neurotrophins are expressed in peripheral tissues, particularly in the vasculature. The better-characterized neurotrophin in vascular biology is the brain-derived neurotrophic factor (BDNF). Its largest extracerebral pool resides within platelets, partly inherited from megakaryocytes and also likely internalized from circulation. Activation of platelets releases vast amounts of BDNF into their milieu and interestingly leads to platelet aggregation through binding of its receptor, the tropomyosin-related kinase B, on the platelet surface. As BDNF is readily available in plasma, a mechanism to preclude excessive platelet activation and aggregation appears critical. As such, binding of BDNF to α2-macroglobulin hinders its ability to bind its receptor and limits its platelet-activating effects to the site of vascular injury. Altogether, addition of BDNF to a forming clot facilitates not only paracrine platelet activation but also binding to fibrinogen, rendering the resulting clot more porous and plasma-permeable. Importantly, release of BDNF into circulation also appears to be protective against adverse cardiovascular and cerebrovascular outcomes, which has been reported in both animal models and epidemiologic studies. This opens an avenue for platelet-based strategies to deliver BDNF to vascular lesions and facilitate wound healing through its regenerative properties. Finally, we summarize relevant new data on this topic presented during the 2023 International Society on Thrombosis and Haemostasis Congress.

Plasma levels of neurotrophin 4/5, NGF and pro-BDNF influence transition to mental disorders in a sample of individuals at ultra-high risk for psychosis

BACKGROUND

Neurotrophins (NTs) and their precursors (pro-NTs) are polypeptides with important roles in neuronal development, differentiation, growth, survival and plasticity, as well as apoptosis and neuronal death. Imbalance in NT levels were observed in schizophrenia spectrum disorders, but evidence in ultra-high risk for psychosis (UHR) samples is scarce.

METHODS

A naturalistic sample of 87 non-help-seeking UHR subjects and 55 healthy controls was drawn from the general population. Blood samples were collected and NT-3, NT-4/5, BDNF, pro-BDNF, NGF, pro-NGF were analyzed through enzyme linked immunosorbent assay (ELISA). Information on cannabis and tobacco use was also collected. Logistic regression models and path analysis were used to control for confounders (tobacco, age, cannabis use).

RESULTS

NT-4/5 was significantly decreased, and pro-BDNF was significantly increased in UHR individuals compared to controls. Cannabis use and higher NGF levels were significantly related to transition to psychiatric disorders among UHR subjects. Increased pro-BDNF and decreased NT-4/5 influenced transition by the mediation of perceptual abnormalities.

CONCLUSIONS

Our study shows for the first time that NTs are altered in UHR compared to healthy control individuals, and that they can be a predictor of transition to psychiatric illnesses in this population. Future studies should employ larger naturalistic samples to confirm the findings.

Glucocorticoids Orchestrate Adult Hippocampal Plasticity: Growth Points and Translational Aspects

The review analyzes modern concepts about the control of various mechanisms of the hippocampal neuroplasticity in adult mammals and humans by glucocorticoids. Glucocorticoid hormones ensure the coordinated functioning of key components and mechanisms of hippocampal plasticity: neurogenesis, glutamatergic neurotransmission, microglia and astrocytes, systems of neurotrophic factors, neuroinflammation, proteases, metabolic hormones, neurosteroids. Regulatory mechanisms are diverse; along with the direct action of glucocorticoids through their receptors, there are conciliated glucocorticoid-dependent effects, as well as numerous interactions between various systems and components. Despite the fact that many connections in this complex regulatory scheme have not yet been established, the study of the factors and mechanisms considered in the work forms growth points in the field of glucocorticoid-regulated processes in the brain and primarily in the hippocampus. These studies are fundamentally important for the translation into the clinic and the potential treatment/prevention of common diseases of the emotional and cognitive spheres and respective comorbid conditions.

The association of brain-derived neurotrophic factor with the diagnosis and treatment response in depression

INTRODUCTION

Recent evidence from the studies evaluating the association between brain derived neurotrophic factor (BDNF) concentration/levels, BDNF Val66Met (rs6265) polymorphism and major depressive disorders, referred as depression, and the association between BDNF levels and/or BDNF Val66Met with the treatment response in depression, is presented.

AREAS COVERED

This mini review focuses on the changes in the peripheral BDNF levels in blood (serum, plasma, platelets) in patients with depression before or after treatment with antidepressant drugs or different therapeutic strategies. In addition, this review describes the recent data on the possible association between different antidepressants/therapeutic strategies and the particular BDNF Val66Met genotypes, evaluating the risk alleles associated with the response in patients with depression.

EXPERT OPINION

BDNF has an important role in the pathophysiology and treatment response in depression. Most data reveal that peripheral BDNF levels are lower before than after antidepressant treatment and might be used as potential biomarkers of therapeutic response. Novel therapeutic strategies should target restoring/increasing BDNF levels.

Neurotrophins: Neuroimmune Interactions in Human Atopic Diseases

Allergic diseases are accompanied by a variety of symptoms such as pruritus, coughing, sneezing, and watery eyes, which can result in severe physiological and even psychological impairments. The exact mechanisms of these conditions are not yet completely understood. However, recent studies demonstrated a high relevance of neurotrophins in allergic inflammation, as they induce cytokine release, mediate interaction between immune cells and neurons, and exhibit different expression levels in health and disease. In this review, we aim to give an overview of the current state of knowledge concerning the role of neurotrophins in atopic disorders such as atopic dermatitis, allergic asthma, and allergic rhinitis.

Distinct conformational changes occur within the intrinsically unstructured pro-domain of pro-Nerve Growth Factor in the presence of ATP and Mg2

Nerve growth factor (NGF), the prototypical neurotrophic factor, is involved in the maintenance and growth of specific neuronal populations, whereas its precursor, proNGF, is involved in neuronal apoptosis. Binding of NGF or proNGF to TrkA, p75NTR , and VP10p receptors triggers complex intracellular signaling pathways that can be modulated by endogenous small-molecule ligands. Here, we show by isothermal titration calorimetry and NMR that ATP binds to the intrinsically disordered pro-peptide of proNGF with a micromolar dissociation constant. We demonstrate that Mg2+ , known to play a physiological role in neurons, modulates the ATP/proNGF interaction. An integrative structural biophysics analysis by small angle X-ray scattering and hydrogen-deuterium exchange mass spectrometry unveils that ATP binding induces a conformational rearrangement of the flexible pro-peptide domain of proNGF. This suggests that ATP may act as an allosteric modulator of the overall proNGF conformation, whose likely distinct biological activity may ultimately affect its physiological homeostasis.

Finding memo: versatile interactions of the VPS10p-Domain receptors in Alzheimer’s disease

The family of VPS10p-Domain (D) receptors comprises five members named SorLA, Sortilin, SorCS1, SorCS2 and SorCS3. While their physiological roles remain incompletely resolved, they have been recognized for their signaling engagements and trafficking abilities, navigating a number of molecules between endosome, Golgi compartments, and the cell surface. Strikingly, recent studies connected all the VPS10p-D receptors to Alzheimer’s disease (AD) development. In addition, they have been also associated with diseases comorbid with AD such as diabetes mellitus and major depressive disorder. This systematic review elaborates on genetic, functional, and mechanistic insights into how dysfunction in VPS10p-D receptors may contribute to AD etiology, AD onset diversity, and AD comorbidities. Starting with their functions in controlling cellular trafficking of amyloid precursor protein and the metabolism of the amyloid beta peptide, we present and exemplify how these receptors, despite being structurally similar, regulate various and distinct cellular events involved in AD. This includes a plethora of signaling crosstalks that impact on neuronal survival, neuronal wiring, neuronal polarity, and synaptic plasticity. Signaling activities of the VPS10p-D receptors are especially linked, but not limited to, the regulation of neuronal fitness and apoptosis via their physical interaction with pro- and mature neurotrophins and their receptors. By compiling the functional versatility of VPS10p-D receptors and their interactions with AD-related pathways, we aim to further propel the AD research towards VPS10p-D receptor family, knowledge that may lead to new diagnostic markers and therapeutic strategies for AD patients.

ProBDNF and Brain-Derived Neurotrophic Factor Prodomain Differently Modulate Acetylcholine Release in Regenerating and Mature Mouse Motor Synapses

The effects of brain-derived neurotrophic factor (BDNF) processing by-products (proBDNF and BDNF prodomain) on the activity of mouse neuromuscular junctions (NMJs) were studied in synapses formed during the reinnervation of extensor digitorum longus muscle (m. EDL) and mature synapses of the diaphragm. The parameters of spontaneous miniature endplate potentials (MEPPs) and evoked endplate potentials (EPPs) were analyzed in presence of each of the BDNF maturation products (both – 1 nM). In newly formed NMJs, proBDNF caused an increase in the resting membrane potential of muscle fibers and a decrease in the frequency of MEPPs, which was prevented by tertiapin-Q, a G-protein-coupled inwardly rectifying potassium channels (GIRK) blocker but not by p75 receptor signaling inhibitor TAT-Pep5. proBDNF had no effect on the parameters of EPPs. BDNF prodomain in newly formed synapses had effects different from those of proBDNF: it increased the amplitude of MEPPs, which was prevented by vesamicol, an inhibitor of vesicular acetylcholine (ACh) transporter; and reduced the quantal content of EPPs. In mature NMJs, proBDNF did not influence MEPPs parameters, but BDNF prodomain suppressed both spontaneous and evoked ACh release: decreased the frequency and amplitude of MEPPs, and the amplitude and quantal content of EPPs. This effect of the BDNF prodomain was prevented by blocking GIRK channels, by TAT-Pep5 or by Rho-associated protein kinase (ROCK) inhibitor Y-27632. At the same time, the BDNF prodomain did not show any inhibitory effects in diaphragm motor synapses of pannexin 1 knockout mice, which have impaired purinergic regulation of neuromuscular transmission. The data obtained suggest that there is a previously unknown mechanism for the acute suppression of spontaneous and evoked ACh release in mature motor synapses, which involves the activation of p75 receptors, ROCK and GIRK channels by BDNF prodomain and requires interaction with metabotropic purinoreceptors. In general, our results show that both the precursor of BDNF and the product of its maturation have predominantly inhibitory effects on spontaneous and evoked ACh release in newly formed or functionally mature neuromuscular junctions, which are mainly opposite to the effects of BDNF. The inhibitory influences of both proteins related to brain neurotrophin are mediated via GIRK channels of mouse NMJs.

ProBDNF as an Indicator of Improvement among Women with Depressive Episodes

Depression is a chronic psychiatric disorder with a heavy socioeconomic burden. Studies on biomarkers are needed to comprehend the pathophysiology of depression and to improve treatment outcomes. Research points to the importance of imbalance between mature brain-derived neurotrophic factor (BDNF) and its precursor, pro–brain–derived neurotrophic factor (proBDNF), in the pathophysiology of mood disorders and the potential neurodegenerative role of calcium-binding protein B (S100B). Our objective was to compare BDNF, proBDNF, and S100B serum levels before and after the treatment of acute depressive episodes and to assess their correlation with the severity of symptoms and history of stress. We also aimed to investigate the differences in BDNF, proBDNF, and S100B levels between depression in the course of bipolar disorder (BD) and major depressive disorder (MDD). We recruited 31 female patients diagnosed with BD or MDD who were hospitalized due to current depressive episodes. The patients had their serum BDNF, proBDNF, and S100B levels evaluated using the ELISA method upon admission and after the symptoms improved, at discharge. We found that proBDNF levels decreased significantly with the treatment (p = 0.0478), while BDNF and S100B levels were not altered significantly. No differences in biochemical parameters between MDD and BD subjects were observed. Consequently, we concluded that a decrease in serum proBDNF levels could be considered a biomarker of recovery from depressive episodes.

DNA methylome perturbations: an epigenetic basis for the emergingly heritable neurodevelopmental abnormalities associated with maternal smoking and maternal nicotine exposure†

Maternal smoking during pregnancy is associated with an ensemble of neurodevelopmental consequences in children and therefore constitutes a pressing public health concern. Adding to this burden, contemporary epidemiological and especially animal model research suggests that grandmaternal smoking is similarly associated with neurodevelopmental abnormalities in grandchildren, indicative of intergenerational transmission of the neurodevelopmental impacts of maternal smoking. Probing the mechanistic bases of neurodevelopmental anomalies in the children of maternal smokers and the intergenerational transmission thereof, emerging research intimates that epigenetic changes, namely DNA methylome perturbations, are key factors. Altogether, these findings warrant future research to fully elucidate the etiology of neurodevelopmental impairments in the children and grandchildren of maternal smokers and underscore the clear potential thereof to benefit public health by informing the development and implementation of preventative measures, prophylactics, and treatments. To this end, the present review aims to encapsulate the burgeoning evidence linking maternal smoking to intergenerational epigenetic inheritance of neurodevelopmental abnormalities, to identify the strengths and weaknesses thereof, and to highlight areas of emphasis for future human and animal model research therein.

ProBDNF Dependence of LTD and Fear Extinction Learning in the Amygdala of Adult Mice

Neurotrophins are secreted proteins that control survival, differentiation, and synaptic plasticity. While mature neurotrophins regulate these functions via tyrosine kinase signaling (Trk), uncleaved pro-neurotrophins bind preferentially to the p75 neurotrophin receptor (p75NTR) and often exert opposite effects to those of mature neurotrophins. In the amygdala, brain-derived neurotrophic factor (BDNF) enables long-term potentiation as well as fear and fear extinction learning. In the present study, we focused on the impact of mature BDNF and proBDNF signaling on long-term depression (LTD) in the lateral amygdala (LA). Hence, we conducted extracellular field potential recordings in an in vitro slice preparation and recorded LTD in cortical and thalamic afferents to the LA. LTD was unchanged by acute block of BDNF/TrkB signaling. In contrast, LTD was inhibited by blocking p75NTR signaling, by disinhibition of the proteolytic cleavage of proBDNF into mature BDNF, and by preincubation with a function-blocking anti-proBDNF antibody. Since LTD-like processes in the amygdala are supposed to be related to fear extinction learning, we locally inhibited p75NTR signaling in the amygdala during or after fear extinction training, resulting in impaired fear extinction memory. Overall, these results suggest that in the amygdala proBDNF/p75NTR signaling plays a pivotal role in LTD and fear extinction learning.

BDNF and pro-BDNF in serum and exosomes in major depression: Evolution after antidepressant treatment

BACKGROUND

The study of clinically related biological indicators in Major Depression (MD) is important. The Brain Derived Neurotrophic Factor (BDNF) appears to play an important role in MD, through its neurotrophic effect, and its levels are significantly decreased. The variation in the serum levels of its precursor proBDNF, which has opposite effects, is not known. Their distribution between serum and exosomes and their evolution during antidepressant treatment is also not known, and may be important in modulating their effects. The aim of this study is to evaluate whether serum and exosome mBDNF and proBDNF levels are altered in patients with MD during antidepressant treatment compared to controls, and their association with clinical improvement and clinical variables.

MATERIALS AND METHODS

42 MD subjects and 40 controls were included. Questionnaires to assess the severity of depression and cognitive impairment and blood samples were collected during the three visits at D0 (inclusion) and 3 and 7 weeks after the start of antidepressant treatment. Assays for mBDNF and proBDNF levels were performed in serum and exosomes by ELISA.

RESULTS

MD subjects had decreased serum and exosomal BDNF levels and increased proBDNF levels at D0 compared to controls. BDNF and pro-BDNF vary in an inverse manner in both serum and exosomes during antidepressant treatment. No relationship of BDNF and proBDNF levels to clinical improvement and depression scales was found.

CONCLUSION

We demonstrated an evolution of those molecules either in serum or in exosomes after MD treatment. These transport vesicles could have a role in the regulation of BDNF.

Isoform-Specific Effects of Apolipoprotein E on Markers of Inflammation and Toxicity in Brain Glia and Neuronal Cells In Vitro

Mutations to the cholesterol transport protein apolipoprotein E (ApoE) have been identified as a major risk factor for the development of sporadic or late-onset Alzheimer’s disease (AD), with the e4 allele representing an increased risk and the rare e2 allele having a reduced risk compared to the primary e3 form. The reasons behind the change in risk are not entirely understood, though ApoE4 has been connected to inflammation and toxicity in both the brain and the periphery. The goal of this study was to better understand how the ApoE isoforms (ApoE2/3/4) confer differential AD-related risk by assessing cell-specific ApoE-related neuroinflammatory and neurotoxic effects. We compared the effects of ApoE isoforms in vitro on human astrocytes, a human immortalized microglia cell line (HMC3), and the human neuroblastoma cell line SH-SY5Y. Cells were treated for 24 h with or without recombinant ApoE2, ApoE3, or ApoE4 (20 nM) and inflammation and toxicity markers assessed. Our results indicated the expression of inflammatory cytokines IL-1β, TNFα, and IL-6 in human astrocytes was increased in response to all ApoE isoforms, with ApoE4 evoking the highest level of cytokine expression. In response to ApoE2 or ApoE3, microglial cells showed reduced levels of microglial activation markers TREM2 and Clec7a, while ApoE4 induced increased levels of both markers. ApoE2 promoted neuron survival through increased BDNF release from astrocytes. In addition, ApoE2 promoted, while ApoE4 reduced, neuronal viability. Overall, these results suggest that ApoE4 acts on cells in the brain to promote inflammation and neuronal injury and that the deleterious effects of ApoE4 on these cells may, in part, contribute to its role as a risk factor for AD.

Peripheral and central nervous system alterations in a rat model of inflammatory arthritis

It is consistently reported that in inflammatory arthritis (IA), pain may continue despite well-controlled inflammation, most likely due to interactions between joint pathology and pain pathway alterations. Nervous system alterations have been described, but much remains to be understood about neuronal and central non-neuronal changes in IA. Using a rat model of IA induced by intra-articular complete Freund's adjuvant injection, this study includes a thorough characterization of joint pathology and objectives to identify peripheral innervation changes and alterations in the spinal dorsal horn (DH) that could alter DH excitatory balancing. Male and female rats displayed long-lasting pain-related behavior, but, in agreement with our previous studies, other pathological alterations emerged only at later times. Cartilage vascularization, thinning, and decreased proteoglycan content were not detectable in the ipsilateral cartilage until 4 weeks after complete Freund's adjuvant. Sympathetic and peptidergic nociceptive fibers invaded the ipsilateral cartilage alongside blood vessels, complex innervation changes were observed in the surrounding skin, and ipsilateral nerve growth factor protein expression was increased. In the DH, we examined innervation by peptidergic and nonpeptidergic nociceptors, inhibitory terminal density, the KCl cotransporter KCC2, microgliosis, and astrocytosis. Here, we detected the presence of microgliosis and, interestingly, an apparent loss of inhibitory terminals and decreased expression of KCC2. In conclusion, we found evidence of anatomical, inflammatory, and neuronal alterations in the peripheral and central nervous systems in a model of IA. Together, these suggest that there may be a shift in the balance between incoming and outgoing excitation, and modulatory inhibitory tone in the DH.

Neutralizing antibody to proNGF rescues erectile function by regulating the expression of neurotrophic and angiogenic factors in a mouse model of cavernous nerve injury

BACKGROUND

Radical prostatectomy induces some degree of cavernous nerve injury (CNI) and causes denervation-induced pathologic changes in cavernous vasculature, regardless of the advances in surgical techniques and robotic procedures. The precursor for nerve growth factor (proNGF) is known to be involved in neuronal cell apoptosis and microvascular dysfunction through its receptor p75NTR .

OBJECTIVES

To determine the expression of proNGF/p75NTR and the efficacy of proNGF neutralizing antibody (anti-proNGF-Ab) in a mouse model of ED induced by CNI.

MATERIALS AND METHODS

Age-matched 12-week-old C57BL/6 mice were distributed into three groups: sham group and bilateral CNI group treated with intracavernous injections of PBS (20 μL) or of anti-proNGF-Ab (20 µg in 20 μL of PBS) on days -3 and 0. Two weeks after treatment, erectile function was measured by electrical stimulation of cavernous nerve. Penis tissues from a separate group of animals were harvested for further analysis. We also determined the efficacy of anti-proNGF-Ab on neural preservation in major pelvic ganglion (MPG) ex vivo.

RESULTS

We observed increased penile expression of proNGF and p75NTR after CNI. Intracavernous administration of anti-proNGF-Ab increased nNOS and neurofilament expression probably by enhancing the production of neurotrophic factors, such as neurotrophin-3, NGF, and brain-derived neurotrophic factor. Anti-proNGF-Ab preserved the integrity of cavernous sinusoids, such as pericytes, endothelial cells, and endothelial cell-to-cell junctions, possibly by controlling angiogenic factors (angiopoietin-1, angiopoietin-2, and vascular endothelial growth factor) and induced endogenous eNOS phosphorylation in CNI mice. And finally, treatment with anti-proNGF-Ab rescued erectile function in CNI mice. Anti-proNGF-Ab also enhanced neurite sprouting from MPG exposed to lipopolysaccharide.

DISCUSSION AND CONCLUSION

The preservation of damaged cavernous neurovasculature through inhibition of the proNGF/p75NTR pathway may be a novel strategy to treat radical prostatectomy-induced erectile dysfunction.

Blockage of p75NTR ameliorates depressive-like behaviours of mice under chronic unpredictable mild stress

The precursor of brain derived neurotrophic factor (proBDNF) and its receptor p75NTR are upregulated in depressive patients and chronic stress-induced depressive animals, suggesting that activation of p75NTR signalling may underlie pathogenesis of depression. In the present study we hypothesize that the blockade of p75NTR may have therapeutic effect on depressive mice under chronic stress. The treatment of mice with the recombinant fusion protein of p75NTR extracellular domain and fragment C of immunoglobulin (p75ECD-Fc) significantly reduced the immobility time in the forced swim test and tail suspension test, and increased the time spent in the central zone in the open field test in mice exposed to chronic unpredictable mild stress (CUMS). p75ECD-Fc treatment also significantly increased the length and density of neuronal dendritic spines in the dentate gyrus and amygdala. Our data indicate that blocking p75NTR signalling can alleviate depressive and anxiety-like behaviours of chronically stressed mice and improve the dendritic spinogenesis of neurons under stress.

Nerve Growth Factor: The First Molecule of the Neurotrophin Family

Neurotrophins (NTs) are molecules regulating differentiation, maintenance, and functional plasticity of vertebrate nervous systems. Nerve growth factor (NGF) was the first to be identified in the neurotrophin family. The long scientific history of NTs provided not only advancement in the neuroscience field but opened new scenarios involving different body districts in physiological and pathological conditions, which include the immune, endocrine, and skeletal system, vascular districts, inflammation, etc. To date, many biological aspects of NTs have been clarified, but the new discoveries are still opening new insights on molecular and cellular mechanisms and systemic effects, also affecting the possible therapeutic application of NTs. This short review summarizes the main aspects of NGF biology and biochemistry, including the role of the NGF precursor molecule, high- and low-affinity receptors and related intracellular pathways, and target cells.

The Chronic Treatment With 5-HT2A Receptor Agonists Affects the Behavior and the BDNF System in Mice

Serotonin 5-HT2A receptors and the brain-derived neurotrophic factor (BDNF) are involved in the pathophysiology and treatment of many psychiatric diseases. However, the interaction between 5-HT2A and BDNF is still poorly understood. In the present paper, the effects of chronic treatment with mixed 5-HT2A/2C receptor agonist DOI, highly selective 5-HT2A agonists TCB-2 and 25CN-NBOH on behavior and the BDNF system have been investigated. Chronic treatment of males of C57Bl/6 mice with DOI, TCB-2 and 25CN-NBOH (1 mg/kg, i.p., 14 days) resulted in desensitization of 5-HT2A receptors. Treatment with 25CN-NBOH significantly increased startle amplitude. At the same time all used drugs failed to affect anxiety, exploratory and stereotyped behavior as well as spatial memory and learning. TCB-2 and 25CN-NBOH increased the BDNF mRNA level. All 5-HT2A agonists increased the proBDNF level but failed to alter the mature BDNF protein level. TrkB and p75NTR mRNA levels were affected by all utilized agonists. All drugs decreased the total level as well as membrane TrkB protein one indicating downregulation of TrkB receptors. All agonists decreased the membrane p75NTR protein level. Thus, we have shown for the first time that the chronic activation of the 5-HT2A receptor with agonists has affected the BDNF system almost on all levels-transcription, proBDNF production, TrkB and p75NTR receptors' level. The obtained data suggested possible suppression in BDNF-TrkB signaling under chronic treatment with 5-HT2A agonists.

Proteolytic cleavage of Slit by the Tolkin protease converts an axon repulsion cue to an axon growth cue in vivo

Slit is a secreted protein that has a canonical function of repelling growing axons from the CNS midline. The full-length Slit (Slit-FL) is cleaved into Slit-N and Slit-C fragments, which have potentially distinct functions via different receptors. Here, we report that the BMP-1/Tolloid family metalloprotease Tolkin (Tok) is responsible for Slit proteolysis in vivo and in vitro. In Drosophilatok mutants lacking Slit cleavage, midline repulsion of axons occurs normally, confirming that Slit-FL is sufficient to repel axons. However, longitudinal axon guidance is highly disrupted in tok mutants and can be rescued by midline expression of Slit-N, suggesting that Slit is the primary substrate for Tok in the embryonic CNS. Transgenic restoration of Slit-N or Slit-C does not repel axons in Slit-null flies. Slit-FL and Slit-N are both biologically active cues with distinct axon guidance functions in vivo Slit signaling is used in diverse biological processes; therefore, differentiating between Slit-FL and Slit fragments will be essential for evaluating Slit function in broader contexts.

Neurotrophin signalling in amygdala-dependent cued fear learning

The amygdala is a central hub for fear learning assessed by Pavlovian fear conditioning. Indeed, the prevailing hypothesis that learning and memory are mediated by changes in synaptic strength was shown most convincingly at thalamic and cortical afferents to the lateral amygdala. The neurotrophin brain-derived neurotrophic factor (BDNF) is known to regulate synaptic plasticity and memory formation in many areas of the mammalian brain including the amygdala, where BDNF signalling via tropomyosin-related kinase B (TrkB) receptors is prominently involved in fear learning. This review updates the current understanding of BDNF/TrkB signalling in the amygdala related to fear learning and extinction. In addition, actions of proBDNF/p75NTR and NGF/TrkA as well as NT-3/TrkC signalling in the amygdala are introduced.

Parkinson's Disease-Associated Changes in the Expression of Neurotrophic Factors and their Receptors upon Neuronal Differentiation of Human Induced Pluripotent Stem Cells

Parkinson's disease (PD) is a neurodegenerative pathology resulting from the degeneration of dopaminergic (DA) neurons in the substantia nigra (SN). Neurotrophic factors (NTFs) and their receptors are key regulators of the survival, differentiation, and development of neurons. However, the role of these factors in the pathogenesis of PD is still unclear. Here, we analyzed the expression of NTFs and their receptors in human induced pluripotent stem cells (iPSCs) derived from the fibroblasts of patients with PD and healthy donors (HDs). Four PD-derived iPSC lines with different mutations and three cell lines from HDs at different stages of neuronal differentiation were used for RT-qPCR analysis and ELISA. We found that the mRNA levels of most analyzed genes were altered in PD-derived cells compared with those in HD-derived cells at all stages. Importantly, irrespective of PD-associated mutations, the mRNA levels of the BDNF and GDNF genes were mostly increased or unchanged in predominantly DA terminally differentiated neurons (TDNs) compared with those in HD-derived cells. Strikingly, in contrast to BDNF and GDNF mRNA levels, BDNF and GDNF protein levels were lower in almost all PD-derived TDNs than in HD-derived cells, thus indicating the dysregulation of NTF expression at the post-transcriptional level. We suggest that this dysregulation is one of the important signs of PD development.

Effects of the selective TrkA agonist gambogic amide on pigmentation and growth of human hair follicles in vitro

The human hair follicle is a neuroendocrine mini-organ that can be used to study aging processes in vitro. Neurotrophins maintain homeostasis in hair biology via the Trk-family of receptors. TrkA, the high affinity receptor for nerve growth factor (NGF), is expressed in hair follicle melanocytes and keratinocytes, where it regulates proliferation, differentiation and apoptosis and may thereby play a role in hair pigmentation and growth. We investigated TrkA expression during the human hair cycle and the effects of a selective high affinity TrkA agonist, Gambogic Amide, on hair pigmentation and hair growth in human hair follicles in vitro. In human scalp skin, TrkA expression was strongest in proliferating melanocytes re-establishing the pigmentary unit in the hair bulb during the early hair growth phase, anagen. During high anagen and in the de-composing pigmentary-unit of the regression phase, catagen, bulb-melanocytes lost TrkA expression and only undifferentiated outer root sheath melanocytes maintained it. In cultured human anagen hair follicles, Gambogic Amide was able to prevent gradual pigment loss, while it stimulated hair shaft elongation. This was achieved by increased melanocyte activation, migration and dendricity, highlighted by distinct c-KIT-expression in melanocyte sub-populations. Our results suggest that Gambogic Amide can maintain hair follicle pigmentation by acting on undifferentiated melanocytes residing in the outer root sheath and making them migrate to establish the pigmentary-unit. This suggests that the selective TrkA agonist Gambogic Amide acts as an anti-hair greying and hair growth promoting molecule in vitro.

Developmental nicotine exposure elicits multigenerational disequilibria in proBDNF proteolysis and glucocorticoid signaling in the frontal cortices, striata, and hippocampi of adolescent mice

Maternal smoking of conventional or vapor cigarettes during pregnancy, a form of developmental nicotine exposure (DNE), enhances the risk of neurodevelopmental disorders such as ADHD, autism, and schizophrenia in children. Modeling the multigenerational effects of smoking during pregnancy and nursing in the first- (F1) and second- (F2) generation adolescent offspring of oral nicotine-treated female C57BL/6J mice, we have previously reported that DNE precipitates intergenerational transmission of nicotine preference, hyperactivity and impulsivity-like behaviors, altered rhythmicity of home cage activity, corticostriatal nicotinic acetylcholine receptor and dopamine transporter dysfunction, and corticostriatal global DNA methylome deficits. In aggregate, these DNE-evoked behavioral, neuropharmacological, and epigenomic anomalies mirror fundamental etiological aspects of neurodevelopmental disorders including ADHD, autism, and schizophrenia. Expanding this line of research, the current study profiled the multigenerational neurotrophic and neuroendocrine consequences of DNE. Results reveal impaired proBDNF proteolysis as indicated by proBDNF-BDNF imbalance, downregulation of the proBDNF processing enzyme furin, atypical glucocorticoid receptor (GR) activity as implied by decreased relative nuclear GR localization, and deficient basal plasma corticosterone (CORT) levels in adolescent DNE offspring and grandoffspring. Collectively, these data recapitulate the BDNF deficits and HPA axis dysregulation characteristic of neurodevelopmental disorders such as ADHD, autism, and schizophrenia as well as the children of maternal smokers. Notably, as BDNF is a quintessential mediator of neurodevelopment, our prior findings of multigenerational DNE-induced behavioral and neuropharmacological abnormalities may stem from neurodevelopmental insults conferred by the proBDNF-BDNF imbalance detected in DNE mice. Similarly, our findings of multigenerational GR hypoactivity may contribute to the increased risk-taking behaviors and aberrant circadian rhythmicity of home cage activity that we previously documented in first- and second-generation DNE mice.

Modulation of the p75 neurotrophin receptor suppresses age-related basal forebrain cholinergic neuron degeneration

Age-related degeneration of basal forebrain cholinergic neurons (BFCNs) is linked to cognitive impairment. The p75 neurotrophin receptor (p75^NTR) has been proposed to mediate neuronal degeneration in aging. Therefore, we tested the hypothesis that modifying p75^NTR function would prevent or reverse aging-related neuronal degeneration using LM11A-31, a small molecule p75^NTR modulator that downregulates degenerative and upregulates trophic receptor-associated signaling. Morphological analysis in mice showed loss of BFCN area detectable by 18 months of age. Oral administration of LM11A-31 from age 15 to 18 months resulted in a dose-related preservation of BFCN area and one month of treatment from 17 to 18 months also preserved cell area. To evaluate reversal of established neuronal atrophy, animals were treated from 21 to 25 months of age. Treatment was associated with an increase of cell size to a mean area larger than that observed at 18 months, accompanied by increases in mean MS/VDB neurite length, as well as increased cholinergic fiber density and synaptophysin pre-synaptic marker levels in the hippocampus. These findings support the idea that modulation of p75^NTR activity can prevent and potentially reverse age-associated BFCN degeneration. Moreover, this may be achieved therapeutically with orally bioavailable agents such as LM11A-31.

Influence of Quadrato Motor Training on Salivary proNGF and proBDNF

Previous studies demonstrated exercise-induced modulation of neurotrophins, such as Nerve Growth Factor (NGF) and Brain-Derived Neurotrophic Factor (BDNF). Yet, no study that we are aware of has examined their change as a function of different training paradigms. In addition, the understanding of the possible training-induced relationship between NGF and BDNF change is still lacking. Consequently, in the current study we examined the effect of a Walking Training (WT) and of Quadrato Motor Training (QMT) on NGF and BDNF precursors (proNGF and proBDNF). QMT is a specifically structured sensorimotor training that involves sequences of movements based on verbal commands, that was previously reported to improve spatial cognition, reflectivity, creativity as well as emotion regulation and general self-efficacy. In addition, QMT was reported to induce electrophysiological and morphological changes, suggesting stimulation of neuroplasticity processes. In two previous independent studies we reported QMT-induced changes in the salivary proNGF and proBDNF levels. Our present results demonstrate that following 12 weeks of daily QMT practice, proNGF level increases while proBDNF showed no significant change. More importantly, while no correlation between the two neurotrophins prior to training was detectable, there was a significant correlation between change in proNGF and proBDNF levels. Taken together the current results suggest that the two neurotrophins undergo a complex modulation, likely related to the different pathways by which they are produced and regulated. Since variations of these neurotrophins have been previously linked to depression, stress and anxiety, the current study may have practical implications and aid in understanding the possible physiological mechanisms that mediate improved well-being, and the dynamic change of neurotrophins as a result of training.

Levels of brain-derived neurotrophic factor in patients with fibromyalgia and chronic low back pain: Results of an aquatic physical therapy protocol

Objectives: This work aims to assess changes in brain-derived neurotrophic factor (BDNF) levels in women after the practice of a specific short duration 10-session aquatic physical therapy protocol in patients with fibromyalgia (FB).

Methods: Case–control study. Thirteen women diagnosed with FB and 11 controls with the same age group, 35–55 years. Patients were evaluated according to the visual analog scale of pain and the fibromyalgia impact questionnaire (FIQ). All were subjected to a short protocol totaling 10 sessions of 40 min twice a week for five weeks. Heart rate and pain were monitored. BDNF levels were measured using enzyme immunoassay.

Results: A statistically significant increase in BDNF values was noted in patients with FB between the pre- and post-10th session assessments (mean of 35.52–41.96; p = 0.041).

Conclusion: BDNF values may present fluctuations during a short duration moderate aerobic exercise protocol, when measured and analyzed in a longitudinal design. Further studies with a more frequent BDNF evaluation could help in understanding its behavior more accurately and are warranted.

Genetically defined fear-induced aggression: Focus on BDNF and its receptors

Brain-derived neurotrophic factor (BDNF), its precursor proBDNF, BDNF pro-peptide, BDNF mRNA levels, as well as TrkB and p75^NTR receptors mRNA and protein levels, were studied in the brain of rats, selectively bred for more than 85 generations for either the high level or the lack of fear-induced aggressive behavior. Furthermore, we have found that rats of aggressive strain demonstrated both high level of aggression toward humans and increased amplitude of acoustic startle response compared to rats selectively bred for the lack of fear-induced aggression. Significant increase in the BDNF mRNA, mature BDNF and proBDNF protein levels in the raphe nuclei (RN), hippocampus (Hc), nucleus accumbens (NAcc), amygdala, striatum and hypothalamus (Ht) of aggressive rats was revealed. The BDNF/proBDNF ratio was significantly reduced in the Hc and NAcc of highly aggressive rats suggesting prevalence of the proBDNF in these structures. In the Hc and frontal cortex (FC) of aggressive rats, the level of the full-length TrkB (TrkB-FL) receptor form was decreased, whereas the truncated TrkB (TrkB-T) protein level was increased in the RN, FC, substantia nigra and Ht. The TrkB-FL/TrkB-T ratio was significantly decreased in highly aggressive rats suggesting TrkB-T is predominant in highly aggressive rats. The p75^NTR expression was slightly changed in majority of studied brain structures of aggressive rats. The data indicate the BDNF system in the brain of aggressive and nonaggressive animals is extremely different at all levels, from transcription to reception, suggesting significant role of BDNF system in the development of highly aggressive phenotype.

Mesenchymal stem cells secretome-induced axonal outgrowth is mediated by BDNF

Mesenchymal stem cells (MSCs) have been used for cell-based therapies in regenerative medicine, with increasing importance in central and peripheral nervous system repair. However, MSCs grafting present disadvantages, such as, a high number of cells required for transplantation and low survival rate when transplanted into the central nervous system (CNS). In line with this, MSCs secretome which present on its composition a wide range of molecules (neurotrophins, cytokines) and microvesicles, can be a solution to surpass these problems. However, the effect of MSCs secretome in axonal elongation is poorly understood. In this study, we demonstrate that application of MSCs secretome to both rat cortical and hippocampal neurons induces an increase in axonal length. In addition, we show that this growth effect is axonal intrinsic with no contribution from the cell body. To further understand which are the molecules required for secretome-induced axonal outgrowth effect, we depleted brain-derived neurotrophic factor (BDNF) from the secretome. Our results show that in the absence of BDNF, secretome-induced axonal elongation effect is lost and that axons present a reduced axonal growth rate. Altogether, our results demonstrate that MSCs secretome is able to promote axonal outgrowth in CNS neurons and this effect is mediated by BDNF.